Pentagon chief Chuck Hagel on Wednesday ordered a 21-day quarantine for all US troops returning from West Africa, calling it a 'prudent' measure to prevent the spread of the Ebola virus.

Pentagon chief Chuck Hagel on Wednesday ordered a 21-day quarantine for all US troops returning from West Africa, calling it a "prudent" measure to prevent the spread of the Ebola virus.

The move means the military is adopting much stricter measures than those in place for civilian health workers sent by the US government to Liberia and Senegal, and the order came amid a debate about how to treat Americans who may have come in contact with those suffering from the deadly disease.

"The secretary believes these initial steps are prudent, given the large number of military personnel transiting from their home base and West Africa, and the unique logistical demands and impact this deployment has on the force," his spokesman Rear Admiral John Kirby said in a statement.

The quarantine was being introduced even though officials say the soldiers will be focused on building medical clinics and will have no contact with those infected with the virus.

But Hagel said the decision was taken partly because military families urged the quarantine.

"This is also a policy that was discussed in great detail by the communities, by the families of our military men and women, and they very much wanted a safety valve on this," Hagel said at an event in the US capital, the "Washington Ideas Forum."

The US Army had already ordered a 21-day quarantine for its troops coming back from Liberia and Senegal. Hagel's order extended the measure to all branches of the military.

Under the decision, Hagel asked the chiefs of the armed services to deliver a detailed plan within 15 days on how to carry out the quarantine. And he directed the chiefs to review the new regimen within 45 days and advise whether to continue with the measures.

Medical experts have sharply criticized recent strict quarantine orders adopted in New York and New Jersey as based on politics rather than science.

President Barack Obama on Tuesday urged Americans to respond to the virus with "facts" rather than "fear."